Lithographic Difficulty Metric for IC Layout Optimization
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Solution Overview
Problem
Current lithographic processes face challenges in identifying and prioritizing 'hard-to-print' patterns for full optimization due to computational intensity and limited applicability of existing methods, especially as critical dimensions in integrated circuit manufacturing approach the resolution limit of lithography tools.
Innovation Solution
A method and computer program product that utilize a lithographic difficulty metric, comprising energy ratio, energy entropy, phase entropy, and total energy entropy factors, to identify and prioritize patterns for full optimization processing by analyzing diffraction orders in spatial frequency space, allowing for efficient selection of unique tiles in a chip layout for optimized printing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If source-mask optimization (SMO) is performed on full chip layout, then lithographic printability is improved, but computational cost becomes prohibitively expensive
Solution Approach 1:
The patent segments the full chip layout into multiple unique tiles or pattern blocks. Each tile is evaluated independently using the lithographic difficulty metric, allowing the computational problem to be divided into smaller, manageable units that can be processed separately and efficiently.
Solution Approach 2:
The patent applies local quality by evaluating only specific regions (tiles with high lithographic difficulty metric values) for full SMO optimization rather than uniformly optimizing the entire chip layout. This focuses computational resources on the most problematic areas while skipping easier-to-print regions.
2Productivity
If predetermined rules are used to identify hard-to-print patterns, then identification speed is improved, but applicability to general cases deteriorates
Solution Approach 1:
The patent changes the parameter basis for identification from fixed predetermined rules to a dynamic lithographic difficulty metric that calculates diffraction order energy distribution. This metric adapts to different pattern geometries and lithographic conditions, providing both speed and general applicability.
Solution Approach 2:
The patent replaces the mechanical rule-based system with a physics-based optical model that calculates diffraction patterns. This substitution allows the system to handle diverse patterns through fundamental optical principles rather than case-specific rules.
3Productivity
If approximate imaging methods are used to identify hard-to-print patterns, then computational speed is improved, but measurement precision deteriorates
Solution Approach 1:
The patent extracts only the essential diffraction order energy information needed for pattern identification, rather than performing complete imaging simulations. By taking out only the critical diffraction metrics, the system achieves fast computation without sacrificing identification accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables fast and effective identification of 'hard-to-print' patterns, allowing for prioritization and full optimization processing, thereby improving the efficiency and cost-effectiveness of the lithographic process, especially for future IC manufacturing where critical dimensions are increasingly smaller.
Implementation Method 1
determining the diffraction orders in spatial frequency space for each of the plurality of layouts
Data Source
AI summary
The present invention provides a lithographic difficulty metric that is a function of an energy ratio factor that includes a ratio of hard-to-print energy to easy-to-print energy of the diffraction orders along an angular coordinate θi of spatial frequency space, an energy entropy factor comprising energy entropy of said diffraction orders along said angular coordinate θi, a phase entropy factor comprising phase entropy of said diffraction orders along said angular coordinate θi, and a total energy entropy factor comprising total energy entropy of said diffraction orders. The hard-to-print energy includes energy of the diffraction orders at values of the normalized radial coordinates r of spatial frequency space in a neighborhood of r=0 and in a neighborhood of r=1, and the easy-to-print energy includes energy of the diffraction orders located at intermediate values of normalized radial coordinates r between the neighborhood of r=0 and the neighborhood of r=1. The value of the lithographic difficulty metric may be used to identify patterns in a design layout that are binding patterns in an optimization computation. The lithographic difficulty metric may be used to design integrated circuits that have good, relatively easy-to-print characteristics.